Exclusion Criteria
-AF
-Conduction disorders (sinus bradycardia, AV blocks)
-Previously prolonged QT
-Negative chronotropic and antiarrhythmic medication
-Electrolyte disturbance
-Myocarditis or MI in follow-up -Impaired clinical situation (renal and hepatic dysfunction, invasive/noninvasive mechanical ventilation requirement, septic shock, acidosis)
AF: atrial fibrillation; AV: atrioventricular; MI: myocardial infarction